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Battery Check procedures

No battery lives forever. Strangely the batteries most worked on live the longest. It's not unusual for batteries in lorries or cabs to live for 6 or 7 years while they only survive 4 years in a car used only once a day for bringing the kids to school. Motorcycle batteries seldom see more than 3 years at all.

But if you suspect the battery what should you check?

Always wear plastic gloves, eye protection and old clothes when working with batteries. Batteries are filled with strong acid that burns paint, skin and eyes. Overloaded batteries can emit highly explosive gases (H2).

1. Visual check:

a) Does the battery leak? Look for large deposits of white powder, burned off paint and the like. Can you see any traces of an impact?

YES = Check for foreign matter under the battery, overtightened hold-down clamp etc AND discard battery. Rince all around with plenty of fresh water before fitting a new one.

b) Open the filling holes and check for acid level. Are all the plates covered with clear liquid? If there's a low it may be caused by: Excessive tension, excessive heat. But all acid-filled batteries need a small top-up from time to time.

NO = Fill up with demineralised water. Do NOT use drinking water. Recharge battery after filling.



2. Check acid density with weight tester.

Any accessory shop has those small inexpensive instruments. They are based on the fact that the acid in a full battery is marginally heavier than in a discharged on. So get one of those, if you already have one rince it with demineralised water before use.

Now note the values you get in the different cells. Ordinary automotive batteries have 6 cells for 12V. The maximum allowed difference between the highest and lowest reading may be 0,03 kg/dm3. Failure of a single cell is the most common fault. That way you have only 10 Volts when starting instead of the correct 12 V. If a single cell shows a low reading almost always the battery is good for recycling.

If all the cells have a low reading the battery is not fully charged. Recharge it overnight and check again.

Density at 27° C Charge To do
1,25 - 1,28 Full Load test can be done
1,20 - 1,24 Partially charged Best charge to full capacity than test
Under 1,20 Discharged Charge immediately

An indication of a shot battery is also if the acid has a brown color and water must be added often.

3. Load test

This can be done by any garage or by most accessory shops. The rule of thumb for resistance-type testers is to test the battery with 3x it's nominal capacity. So a small standard 45AH battery is tested wit a load of 135 Amps for 10 seconds. The drop in voltage must be in the tolerances given by the battery manufacturer.

Note: This test makes only sense if all your cells show an acid density of 1,25 or higher.

A special thanks to Varta Germany who provided us with the pictures and datas.